The present invention relates generally to the field of communication networks, and, more particularly, to communication between networks that use different address domains.
One aspect of the evolution of cable television has been the development of hybrid fiber coax (HFC) networks. Instead of being based entirely on coaxial cable, HFC networks generally include optical fiber cable between the head end and local serving nodes. Each local serving node typically includes a media translator to convert the optical signal into an electrical signal, which is then carried to customers via traditional coaxial cable spans. Cable television companies, or multiple system operators (MSOs) as they are often called, have upgraded many of their existing coaxial cable networks to HFC to take advantage of reduced maintenance costs and improved bandwidth of the optical fiber cable.
With the growth of the Internet, however, MSOs may seek to leverage their investment in these HFC networks to provide more than just cable television programming. The ubiquitous nature of the HFC based cable television network is advantageous in that high-speed data service may be provided to a large segment of the population without the need to install new network infrastructure. As part of providing customers with data-over-cable service, a cable modem is generally used to modulate and demodulate signals passed between the cable television network and the customer premises equipment (CPE) or hosts.
Traditionally, when a customer purchases a cable modem to access an MSOs cable network, a protocol known as dynamic host configuration protocol (DHCP) is run on the cable modem and the hosts (i.e., CPE) at the customer""s home or business to obtain Internet Protocol (IP) addresses that are compatible with the MSOs cable network. Unfortunately, a customer may already have a local network environment in place, such as an Ethernet network, which may or may not be compatible with the address domain used in the MSOs cable network. Moreover, a customer may already have additional external network addresses defined for their hosts to access the Internet or another local or wide area network. As a result, a customer may need to reconfigure their local network by eliminating existing external network addresses and/or by adding the new addresses for the MSOs cable network.
One approach to connecting a local network to an external network without the need to reconfigure the local network is known as network address translation (NAT). Through NAT, a local network may be isolated from an external network by defining a single external network address, which is then used by all entities in the external network for communicating with a host located on the local network. In general, NAT works by storing most or all of the local network addresses in a table, which a gateway or firewall then uses to map to the single external network address. From a point of view outside of the local network, all of the hosts on the local network have the same address (i.e., the external network address defined for NAT). Information destined for the respective hosts is, therefore, routed by the gateway or firewall based on the media access control (MAC) address, local network port number, or other host identification information.
While NAT may allow the local network address configuration to remain intact while providing access to an external network, NAT may also shield knowledge regarding the configuration of the hosts on the local network from an operator or administrator residing on the external network. For example, if the MSO wishes to charge for their service based on the number of hosts on a customer""s local network, then the MSO could not rely on the number of external network addresses assigned to the local network to determine the number of hosts because NAT uses only one external network address to service the customer""s entire local network. As a result, the MSO may need to visit the customer periodically to examine the customer""s local network configuration to generate billing information.
Consequently, there exists a need for improvements in connecting a local network to an external network that uses a different address domain than the local network.
According to embodiments of the present invention, a local network that includes one or more hosts and has a local address domain associated therewith may communicate with an external network having an external address domain associated therewith through a network interface device. The local addresses of the hosts on the local network may be learned and then external addresses may be obtained for each of the learned hosts. Information may be sent from the external network to a host on the local network using the external address associated with the host as a destination address. The external address used as the destination address for the host may then be translated into the local address for the host. Similarly, information may be sent from a host on the local network to the external network using the local address as the source address. The local address used as the source address by the host may then be translated into the corresponding network address that has been obtained for that host.
The present invention may serve as a proxy by translating local addresses into external addresses and vice versa for communication between hosts on the local network and entities in the external network. Unlike systems that use Network Address Translation (NAT) in which multiple local addresses may be mapped to a single external address, the present invention may provide a unique, one-to-one correspondence between the local addresses and the external addresses associated with the hosts. Advantageously, an administrator or operator, such as a multiple service operator (MSO), that resides in the external network may monitor the number of hosts that are in service on the local network through the external addresses that are assigned to the hosts. This may allow the external network administrator to bill for their service based on the number of hosts on a customer""s local network without the need to periodically send a representative into the field to inspect the customer""s local network.
In addition, by providing address translation at the interface of the local network with the external network, the local network need not be reconfigured through the elimination of existing local addresses and/or the addition of new external network addresses into the local network. Thus, the present invention may allow a local network to communicate with an external network while isolating the local network from the details of the external network configuration (i.e., address domain). This aspect of the present invention may facilitate xe2x80x9cplug-and-playxe2x80x9d access of the external network from the point of view of hosts on the local network. Accordingly, the need for site visits by technicians associated with the external network operator (e.g., the MSO) to establish external network service when a new host is added to the local network or for initially establishing external network service to the local network may be reduced or even eliminated.
In accordance with various embodiments of the present invention, the local addresses of the hosts on the local network may be learned in alternative ways. For example, a message may be asynchronously received from a host that contains that host""s local address. Alternatively, a request that the hosts respond with their respective local addresses may be broadcast on the local network. A message may then be received from each of the responding hosts containing that host""s local address. Yet another approach to learning the local addresses of the hosts on the local network may involve storing a list of pre-defined local addresses for the hosts on a computer-readable storage medium. The local addresses may then be read from this stored, pre-defined list.
In accordance with another embodiment of the present invention, the external addresses for the learned hosts may be obtained by sending an external address request to a dynamic host configuration protocol (DHCP) server for each learned host and then receiving an external address from the DHCP server in response to each request. If the external address is an Internet Protocol (IP) address, then, preferably, the external address request contains the media access control (MAC) address of the network interface device and an IP address of all zeros.
Thus, in summary, the present invention may provide a local network with plug-and-play access of an external network while allowing administrators of the external network to have easier access to information with respect to the configuration of the local network, which may facilitate billing for services based on the number of hosts on the local network.